The present invention relates to a stereo sound field enlarging circuit for enlarging a stereo sound field.
A conventional stereo sound field enlarging circuit is arranged as shown in FIG. 1. In the circuit, the difference signal between two signals A and B, which are applied to respective left and right input channel input terminals L and R, is obtained. The difference signal thus obtained is applied to a sound field enlarging circuit, composed of a delay circuit having a delay time .tau. and a phase shifter imposing a phase shift .psi., so that it is phase-shifted and time-delayed. The resultant signals are added, in an optional ratio, to the respective original left and right channel input signals A and B, as a result of which left and right output signals A' and B' are provided.
When reproduced, these signals cause the listener to perceive the reproduced sound as if the sound field were enlarged.
However, the delay circuit and the phase shifter of the sound field enlarging circuit 1 are intricate components and accordingly high in manufacturing cost. Especially, a circuit employing a BBD (bucket-brigade device) as the delay circuit has a considerably high manufacturing cost. Furthermore, perceived natural enlargement of the sound field cannot be obtained without setting the delay time .tau. and the amount of phase shift .psi. to suitable values, which are difficult to determine, and it is considerably difficult to obtain an output from the circuit 1 of sufficient bandwidth to select addition ratio. Especially in a circuit using a BBD, the bandwidth is narrow, and the amount of data available to characterize the directivity of the reproduced sound is small.